Posts Tagged ‘stinkbug’

I have seen a great deal of stink bug damage to tomato fruit this year-more than usual (Fig. 1). The fruit has the characteristic white spots that when peeled back reveal spongy white areas. As the fruit turns red these white areas turn yellow (Fig. 1). When adults, or especially nymphs, feed on the fruit they create a star burst pattern in the surface of the fruit. I guess the surprise is that I have found very few if any Brown marmorated stink bugs (BMSB) in any of these tomato fields. Almost all of the stink bugs have been brown stink bugs (Euschistus spp), although lately (last 2 weeks) I have seen more green stink bugs. There have been very few reports or observations of BMSB being much of a problem so far this year in vegetables. Adult brown stink bugs are grayish-yellow to light brown with dark punctures on their back (Fig. 2). They DO NOT have two white spots on their antenna as do BMSB. Adults overwinter in woods, fence rows and under the bark of trees. A female oviposits a total of about 60 eggs over the summer. The nymphs, which are pale green, develop through five instars and require about one month for development. Because the adults are strong fliers they rapidly can move between hosts. Brown stink bugs are very difficult to scout for and often the only thing that is seen is the damage they cause to large green or ripening fruit. Stink bugs are difficult to control even when found as it takes several applications of insecticide to reduce their numbers (see the Commercial Vegetable Production guide for recommendations). Some of the most heavily fed upon fruit had very dark areas that when cut into appear as a dry rot (Fig. 3). What microorganisms are in this dry rot area is something we are looking into. It appears that our native stink bugs can inject microorganisms almost as readily as do BMSB when they feed.

This is the time of year that we start to see pod disorders in early planted lima beans. This includes partially filled, misshapen, and yellowing pods and irregular, dimpled, or misshapen seed. These disorders are most commonly related to problems with seed development in the pod, either due to incomplete pollination or direct piercing/sucking insect damage to the seed.

Due to the high heat, we are also seeing high amounts of pod drop. In one early planted field that I looked at last week there was fair pod set. This week, virtually all pods had dropped off of the plants. These plants are now reflowering and have the potential to produce a later set. This phenomenon also occurred last year where the consistent high heat did not allow for pod set until August, delaying harvest but still allowing for a good yield in earlier planted lima beans. What is not desired is a split set. The occurs when there is enough heat or drought stress to abort some flowers or pods, but not all of them , and the plant then reflowers in less stressful weather. This causes both mature and immature pods on the plant at the same time, making harvest decisions difficult.

Tracy Leskey (USDA/ARS) provided the following report: “It appears that the beginning of Brown Marmorated Stink Bug (BMSB) immigration and dispersal into commercial orchards has begun in earnest in both WV and MD. Crews out scouting reported large numbers of BMSB in managed peach trees. Not surprisingly, bugs were most dense in the peripheral zone of the plots bordering wild habitat, but not necessarily anywhere near structures. Estimates of bug density were in the vicinity of 3 bugs per tree in border rows, and feeding injury was very fresh but clearly evident.”

Field Corn
We just received word from EPA that they did approve Delaware’s Section 18 emergency use request for Avipel® Hopper Box (dry) Corn Seed Treatment for the protection of field corn seed from consumption by black bird and crows. The effective dates of the Section 18 are April 20, 2011 – April 18, 2012. You can access the label on line at http://www.arkionls.com/. Producers are required to have a copy of the label in their possession to use the product. It is anticipated that product will be in the area this week for use by producers.

Wheat
This week we have had a number of calls about stink bugs and their impact on wheat. Some feel numbers are higher than normal and others think it is a typical year. In general, only a few brown marmorated stink bugs (Halyomorpha halys) have been found with the predominant species being native brown stink bug (Euschistus servus). In years past, we have seen brown stink bugs in wheat. After talking with entomologists in the region, we all feel that more work needs to be done to see if there is an impact from the boot through dough stages. Unfortunately, little is known about the impact of stink bugs on wheat on our area. In VA and North Carolina they feel they are seeing more each spring — mostly native browns but they also feel that wheat could become an early host for brown marmorated (BMSB). Our colleagues at the University of Maryland ( Cerruti Hook and Galen Dively) currently have replicated plots established and will be looking at the impact of BMSB on wheat, so we will know a lot more after the 2011 season. There is information on the internet from states to our south (Mississippi and Arknsas); however, at this point we do not know if that information applies to our area and much of the work was done in the 1980s. One of the concerns we have had is the ability of both species to move from wheat into corn and soybeans fields and this is one of the projects we in Delaware will be working on in 2011.

This has been one of the worse years for stink bug damage in tomatoes that I have seen in a while. Just about every field I walk into has at least some damage while others have severe damage (>35% tomatoes not marketable). Cloudy spot of tomato fruit is caused by the feeding of various species of stink bug (SB). On green fruit the damage appears as whitish areas with indistinct borders (Fig. 1). Individual spots may be 1/16 – 1⁄2 inch in diameter; or, the spots may merge and encompass a large area of the fruit surface. On ripe fruit the spots are golden yellow (Fig. 1). Peeling back the skin shows these areas as white shiny, spongy masses of tissue (Fig.1). This damage is most common from late July or early August until the end of the season, concurring with the activity and feeding of stink bugs. SBs are often difficult to see and usually go unnoticed as they spend much of the day on the ground beneath tomato plants, which results in monitoring problems. Only a few are necessary to cause the appearance of cloudy spot on many tomato fruit. Brown marmorated stink bugs (Fig. 2) as well as leaf-footed (Fig. 3) and tarnished plant bugs also have been observed in larger than usual numbers in tomato fields. The brown marmorated SB may be responsible for some of the more severe feeding damage observed in some tomato fields. The leaf-footed and tarnished plant bugs usually do not do as much damage to fruit as the larger stink bugs. Feeding damage by the immatures of any of the stink bugs often appears as yellow “star-bursts” on red fruit (Fig. 4), which causes a very small shallow white spongy area under the star-burst (Fig. 5).

Stink bugs and tarnished plant bugs usually move into the edges of tomato fields and seldom are found in the interior of the fields, suggesting that spraying the edges of fields could be used as a control tactic. Stink bugs and especially the leaf-footed and tarnished plant bugs, tend to move into tomato fields when preferred hosts that are adjacent to the fields are disturbed or dry out.

This is an extremely difficult pest to monitor and control. There are no good methods of monitoring these pests. Traps do not work well except for just a few species of stink bug, visually scouting for them has proven to be unreliable and too time consuming. Usually SB damage is only a nuisance, but this year it has resulted in large losses in some fields. Growers who have had damage before from stinkbugs may want to examine the edges of their fields carefully starting in mid-June for tomatoes with cloudy spot. If it is a dry year as this year has been, it would probably be best to start in early June checking for damage. There are some acceptable chemical choices for stink bug control. Pyrethroids (Warrior II, Baythroid XL, Mustang MAX), Venom, Leverage, Voliam Xpress, or Tombstone can be used to reduce damage. It should be understood that none of the chemicals will give complete control, but will reduce damage significantly compared with no chemical usage.

A few weeks ago some growers contacted me about a very small bug that was all over their organic fields of various vegetables. It took me awhile to find out what it was as it seemed recognizable, but did not fit any real pest I was familiar with. On one farm the nymphs were all over every vegetable and were feeding most heavily on eggplant—actually killed many plants. This small bug was the Twice stabbed stink bug, Cosmopepla lintnerianaalso known as the Wee Harlequin Bug or Two-spotted stink bug (fig. 1). It is a very small (5-7 mm) bug (fig. 2). The body is black with a red band crossing the width of the insect’s shoulders (pronotum) and a short red stripe along the midline. These markings are sometimes orange or yellow. The pointed back of the bug (scutellum) has two red spots near the tip of this triangular body part (fig. 1). The tips of the wings are clear or white when overlapped. The nymphs have a remarkably similar color pattern as the adults, but lack wings. It can be found throughout much of North America. It has a very wide host range that includes mostly weed species such as thistles, mints, goldenrods, ragweeds, pigweeds as well as vegetable crops such as crucifers, brassicas, tomatoes, eggplants etc. The bugs feed by sucking sap from the plant. Females lay eggs in clusters on host plants and guard them. Adults overwinter under leaf litter in the field or woods.

The odd thing was that there were literally hundreds of the nymphs crawling over everything in the one vegetable field. They even appeared under row cover in some areas of the field. The best I can figure is that the adults laid eggs on the weeds next to the tilled part of the field and when this area was tilled later in the season the eggs survived and were able to hatch and the nymphs suddenly appeared out of the ground. Organic controls did a poor job of controlling even the smaller nymphs. This bug has been an occasional nuisance in vegetable fields, why it is so prominent this year is unknown.